Undersea telecommunications cables frequently must have armor protection to safeguard against natural and man-caused risks which would damage or destroy an unprotected core. Armor usually is provided by one or more lays of galvanized steel wires around the core and its jacketing.
Use of armor wires, however, risks damage or structural deformation to the cable due to twisting motion caused by torsion which the cable and core undergo during installation. Some armored submarine cables of the prior art mitigate the risk of torsional damage by providing torque-balance, a design expedient which counters the twisting tendency. Using a torque-balanced cable throughout a system reduces overall the risk of such damage, which is highly desirable because torsional damage frequently occurs during installation when it is difficult or impossible to detect.
Despite the advantage of torque-balanced cable in avoiding risks of twisting damage, however, relatively little torque-balanced cable has been installed in undersea telecommunications plant. One reason is its poor shipboard storage and handling properties and specifically, its tendency to form loops or kinks if the cable is coiled in small diameters. Kinks are manifestations of the relieving of severe bending stresses in the cable; and in themselves they adversely affect the cable's structural integrity. As a result, the looping tendencies of present designs of armored torque-balanced cable have substantially reduced its potential applications in undersea plant, both military and commercial.
Undersea cable designs capable of being coiled in small diameters without kinking are desirable for the further reason that more efficient use of cable storage volume on board ship can thereby be made, which in turn can generate cost reductions in the installation. The "figure-8" cable coiling configuration typically used shipboard is an example of wasteful use of storage space.
If torque balance is to be included in any segment of an undersea cable system, it is desirable that the entire system be torque-balanced, since otherwise transition cables are required to couple one cable type to another. By using a torque-balanced system, however, no transition cables are needed; and the costs and complexities of cable system installation are reduced.